Ground the chassies in all your things ( at least tie them together, don't forget the record player) and then have at least one of them connected to ground in the outlet.The phono cable is sensitive ( more or less depending on brand of cable) for both electric andmagnetic fields, route it as far from other power cables as possible. Don't collect excess cable in a roll.

Minor clarification. If any of your gear has a three prong plug, and it is plugged into the AC outlet ground, a separate ground wire to the third outlet pin or the screw in the outlet plate will cause a ground loop. This is more critical in a phono system than in one with only line level sources but is worth remembering.

This is a mostly vintage system. Pas2 pre, Dynaco ST70 amp wharfedale speakers. none of which have the ground prong of course. They are plugged into an APC surge protection bar. I also have a DAC connected to the aux input that is connected to a computer via USB. Turntable is Technics with the original power cord and RCA cord/jacks. None have the 3rd prong. The only thing that does is the APC power cord. The hum is only when the Pre is set to Phono.

If your Technics turntable has a separate ground wire, attach it to one of the chassis screws on your pas2. If that write is not attached there will be a lot of humming. It is attached to the tone arm separate from the RCA plug ground. Tony